This invention pertains to multiple layer packaging materials and containers made with those packaging materials. The containers are typically made by heat sealing facing portions of films to each other about a common periphery to form an enclosure, but leaving one side of the enclosure open. A product is then inserted into the container and the open side of the container is sealed closed. The closure of this last side completes the closure of the container.
Alternately, a package may be made from, for example, a receptacle made by thermoforming a sheet, with a non-formed film used as a lid closure over the receptacle.
For use with some products, it is desired that the packaged product be capable of being boiled, as in boiling water, after the package is sealed closed with the product in it. It is this particular market and problem that the invention addresses.
There are available, to the market, certain sheet structures which are capable of handling boiling temperatures. These include, for example, structures which are made for retort pouch applications. These structures are typically of the order of 6 to 8 mils thick, and may contain a metal foil. Another family of structures, of approximately the same thickness includes an outer layer of nylon, a second layer of ethylene vinyl alcohol, a third layer of nylon, a fourth layer of adhesive and a fifth layer of a sealant material.
While the above structures may be useful as regards retort pouch applications, they are prohibitively expensive for use with less valuable products. To the present time, it is not seen that there is available a film for making boilable containers, such as bags, at an economical cost, which containers may thus be used for lower priced products.
It is an object of this invention to provide a novel and economical film which can be made into a boilable container and wherein the contents of the container may expand significantly at boiling temperature; the container being capable of withstanding the boiling process without rupture.
It is a particular object of the invention to provide a packaging container which can be sealed with a moderate amount of gas in it and subsequently boiled without rupture of the package.
It is yet another object of the invention to provide a method of packaging a product in a container where it is acceptable to include an amount of air in the container and where the air does not cause rupture of the container on subsequent boiling of the container.